Table of Content

12 November 2013, Volume 39 Issue 11

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Genetic Diversity Analysis of Widely-planted Soybean Varieties from Different Decades and Major Production Regions in China

WANG Cai-Jie,SUN Shi,JIN Su-Juan,LI Wei,WU Cun-Xiang,HOU Wen-Sheng,HAN Tian-Fu

Acta Agron Sin. 2013, 39(11):  1917-1926.  doi:10.3724/SP.J.1006.2013.01917

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The genetic diversity of widely-planted soybean varieties released after 1940s in Northeast China and Yellow-Huai-Hai Rivers Valley (YHH)were analyzed by 125 simple sequence repeats (SSR) markers, which were related to the important traits including yield, quality, stress tolerance and adaptability. The results showed that the average polymorphism information content (PIC) from north part of Heilongjiang province, south and middle parts of Heilongjiang province, Jilin and Liaoning provinces and Yellow-Huai-Hai Rivers Valley were 0.414, 0.469, 0.522, and 0.562, respectively. Except for the varieties from the north part of Heilongjiang province, the varieties released after 1980 in the other three regions had higher PIC than those released before 1980. Based on similarity proposed by Nei and Li, we classified the tested soybean varieties into three major groups by the cluster analysis, corresponding with the original places of the varieties. The varieties from the Northeast and YHH were classified into two major groups respectively, except for Jidou 12, a variety from northern YHH, which was classified into an independent group. In the Northeast, varieties of Heilongjiang were classified into one subgroup and those from Jilin and Liaoning provinces another subgroup, indicating that the widely-planted varieties from the same region were apparently homogenized.

Resistance Spectrum Difference between Two Broad-spectrum Blast Resistance Genes, Pigm and Pi2, and Their Interaction Effect on Pi1

YU Miao-Miao,DAI Zheng-Yuan,PAN Cun-Hong,CHEN Xi-Jun,YU Ling,ZHANG Xiao-Xiang,LI Yu-Hong,XIAO Ning,GONG Hong-Bing,SHENG Sheng-Lan,PAN Xue-Biao,ZHANG Hong-Xi,LI Ai-Hong

Acta Agron Sin. 2013, 39(11):  1927-1934.  doi:10.3724/SP.J.1006.2013.01927

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Pigm, an R gene to rice blast disease, is either allelic or tightly linked to Pi2. In this study, a series of near-isogenic lines (NILs) containing Pigm and Pi2 under four genetic backgrounds of rice cultivars were established, respectively. The results from inoculating with 204 representative races at seedling stage showed that the resistance frequency of NILs carryingPigm and Pi2 all reachedmore than70%, but the overlapping degree of resistance spectrum between them was only 54.4% to 65.7%, and the resistance frequencyof hybrids pyramiding Pi1/Pigm and Pi1/Pi2 was more than 90%. Disease development from artificial inoculation at heading stage and natural induction in disease nursery showed consistent trend with that from inoculation at seedling stage. Agronomic traits of most NILs were similar to those of recurrent parent, indicating that the target region contains few linkage drags. In conclusion, Pigm is a broad-spectrum blast resistance gene possessing significant resistance spectrum difference from Pi2, and holds important value for rice blast breeding.

Genetic Analysis of Vegetative Ground Cover Rate in Winter Wheat Using Digital Imaging

XIAO Yong-Gui,LIU Jian-Jun,XIA Xian-Chun,CHEN Xin-Min,Matthew REYNOLDS,HE Zhong-Hu

Acta Agron Sin. 2013, 39(11):  1935-1943.  doi:10.3724/SP.J.1006.2013.01935

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Vegetative vigour is an important physiological trait and selection for greater seedling vigour is a goal of breeding programs, especially in rain-fed regions. This study aimed to identify the genetic variation of early vigour, determine the agronomic traits most closely associated with seedling growth, and detect the major gene-containing region of early vigour in winter wheat. Twenty-eight cultivars and advanced lines at two planting densities (240 plants m^-2 and 360 plants m^-2) were grown in Jinan during 2009–2010 and 2010–2011 cropping seasons, with randomized complete block design of three replications. Whole-genome association mapping was employed to identify the chromosome region controlling early vigour using 921 Diversity Array Technology (DArT) and 83 SSR markers. Early vigour was evaluated with vegetative ground cover rate via implementation of photographic image analysis, whereby computer analysis was used to determine percentage ground cover. Significant differences of ground cover rate between two planting densities were detected in pre-winter period, erecting and booting stages, but not in early stem elongation stage. Ground cover rate in erecting stage was significantly and positively associated with maximum tiller number (r = 0.76, P < 0.01), leaf area index (r = 0.74, P < 0.01), spike number (r = 0.73, P < 0.01), and grain yield (r = 0.73, P < 0.01). Twelve gene-containing regions for vegetative ground cover rate were detected in two seasons. Most of the regions conditioning the vegetative ground cover rate were not affected by the developmental stages. Ten gene-containing regions identified were consistent with previously reported QTLs for seedling traits, grain yield and disease resistance. Three regions on 5BL, 6AS, and 6BL were the same as previously reported loci for seedling traits. Therefore, there is sufficient genetic variation to increase early vigour in winter wheat, and early vigour could be quickly measured through digital image analysis.

Cloning, Characterization, and Functional Analysis of TaWRKY44 Gene from Wheat

WANG Rui,WU Hua-Ling,WANG Hui-Fang,HUANG Ke,HUO Chun-Yan,NI Zhong-Fu,SUN Qi-Xin

Acta Agron Sin. 2013, 39(11):  1944-1951.  doi:10.3724/SP.J.1006.2013.01944

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WRKY transcription factors are specific in plants and related in response to stress as well as plant development. In this study, we cloned the full-length cDNA of a new WRKY transcription factor gene, TaWRKY44, from wheat (Triticum aestivum L.). The open reading frame of TaWRKY44 is 897 bp in length, which encodes 298 animo acid residues. The semi-quantitative RT-PCR result indicated that TaWRKY44 was highly expressed in leaf, and responsive to drought and clod stresses. TaWRKY44 over-expressed lines of Arabidopsis exhibited smaller leaves, shorter leaf petioles, and smaller leaf epidermis cell than the wild type. In addition, the transgenic lines were more sensitive to abscisic acid, drought, and salt stresses. These results indicated TaWRKY44 could be a negative regulator in stress signal transduction pathway.

Characteristic and Function Analysis of a Copper Ion Binding Protein, AtBCB Interacting with G Protein α Subunit GPA1 in Arabidopsis thaliana

ZHANG Xiao-Hong,XU Peng-Bo,GUO Meng-Meng,XU Zhao-Shi,LI Lian-Cheng,CHEN Ming,MA You-Zhi

Acta Agron Sin. 2013, 39(11):  1952-1961.  doi:10.3724/SP.J.1006.2013.01952

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Heterotrimeric G protein, including three subunits of α, β, and γ, is involved in a lot of signaling pathways in plants. It receives extracellular signals via G-protein coupled receptor (GPCR) and transmits them to the downstream effectors by the three subunits. Till now, the downstream effectors and signaling pathway related to G-protein complexes have been rarely reported. Furthermore, identifying more novel G protein effectors would be helpful to elucidate signaling pathway associated with the G protein complex. In order to find some novel effectors, G protein α subunit (GPA1) was used as bait to screen interaction protein in Arabidopsis by the split-ubiquitin screening system in this study. One of the GPA1-interacting proteins was identified as copper ion binding protein,AtBCB. The interaction betweenGPA1 and AtBCB was verified on cell membrane by BiFC (bimolecular fluorescence complementation). The expressions of GPA1 and AtBCB were confirmed to be induced by aluminium stress. To study the function of the two genes, we treated Arabidopsis mutant gpa1-4 and bcb, in which GPA1 and AtBCB were knocked out, with 100 µmol L^–1 Al³⁺, respectively, and then measured MDA (malonaldehyde) content in roots. The results showed that MDA content in both mutant and WT (wild type) under normal condition was no significant difference, but when exposured to 100 µmol L^–1 Al³⁺ the content in gpa1-4 was lower than that in WT (P<0.05), and it in bcb was higher than that in WT (P<0.01). Furthermore, the expression patterns of three responsive genes ofALMT1, ALS1 and ALS3 to aluminum toxicity were analyzed by Real-time PCR. The results showed that no matter the condition with or without aluminum stress, the expression of ALS1 and ALS3 appeared no significant difference in the mutants and WT. However, in the treatment with less than 100 µmol L^–1 Al the expression level of ALMT1 ingpa1-4 was higher than that in WT, and the expression level of ALMT1 inbcbwas lower than that in WT. In short, GPA1 and AtBCB directly interact in the cell membrane, and regulate the expression of the downstream gene of ALMT1. In the tolerance process to aluminum stress in plants, GPA1 plays negative role but AtBCB has positive effect.

Cloning and Functional Analysis of GarTHA Gene from Gossypium aridum

FAN Xin-Qi,LIU Zhang-Wei,FENG Juan,XU Peng,ZHANG Xiang-Gui,SHEN Xin-Lian

Acta Agron Sin. 2013, 39(11):  1962-1969.  doi:10.3724/SP.J.1006.2013.01962

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Salinity stress is one of the most important factors that impede the growth and development of various crops. Some Gossypium wild species with tolerance to high salinity are valuable germplasm resource for studying salt tolerance mechanism in Gossypium and improving salinity resistance in upland cotton. In the previous study, we obtained a differential expression fragment by comparing differential expression transcript under stress treatment in diploid G. aridum species using cDNA-AFLP technique. In this study, using the partial cDNA sequences as queries, the Gossypium EST database was screened and the corresponding cDNA sequence containing a complete ORF was assembled. As a result, a novel gene, encoding G. aridum threonine aldolase, was cloned. The gene was designated as GarTHA (G. aridum THA;GenBank accession number: KC167360). The ORF of GarTHA was 822 bp encoding 273 amino acid residues with a predicted molecular weight of 82.57 kD and a predicted isoelectric point of 4.89. The GarTHA showed the highest similarity of 84.6% with poplar PtTHA. To characterize its putative function, we transgenic the ORF of GarTHA gene driven by rd29A promoter into Arabidopsis. The growth of transgenic plants was observed under salinity stress. The seed germination rate and root length of transgenic Arabidopsis were significantly higher than those of the wild type plants under salt stress. The results showed that GarTHA gene could improve salt resistance in plants.

Phenotypic and Genetic Analyses of a Novel Adaxially-rolled Leaf Mutant in Rice

XIE Zhi-Wei,SUN Wei,YIN Liang,ZHAO Jin-Feng,YUAN Shou-Jiang,ZHANG Wen-Hui,LI Xue-Yong

Acta Agron Sin. 2013, 39(11):  1970-1975.  doi:10.3724/SP.J.1006.2013.01970

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Leaf is an important organ for photosynthesis. Moderate rolling of leaves can facilitate the improvement of plant’s population structure and enhance light-use efficiency, which is very important in ideotype breeding of rice. In the present study, in order to systematically dissect the molecular mechanism of leaf morphogenesis and development, one ethyl methylsulfone (EMS) -induced rice (Oryza sativa L.) mutant with adaxially-rolled leaf, namely s1-145, was characterized. This mutant exhibited higher chlorophyll content, normal plant height and fertility. Genetic analysis indicated that the mutant was controlled by a single recessive gene. The mutated gene of s1-145 was fine mapped within a 90 kb interval between two indel markers R2-34.70 and R2-34.79 on the long arm of chromosome 2 in rice. These results provide a basis for the final cloning and functional analysis of the leaf-rolling gene, as well as gene resource and plant material for rice ideotype breeding.

Cloning and Expression Analysis of Soybean Homoserine Kinase (GmHSK) Gene at the Whole Growth Period

WANG Jia-Lin,JIANG Wei,YU Yan,LIU Chun-Yan,CHEN Qing-Shan,HU Guo-Hua

Acta Agron Sin. 2013, 39(11):  1976-1982.  doi:10.3724/SP.J.1006.2013.01976

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Homoserine kinase (HSK), the forth enzyme in the aspartate pathway, plays a key role in the biosynthesis for lysine, methionine, threonine, and isoleucine in higher plants. A HSK gene, termed GmHSK was cloned from soybean Williams 82 which contains a 1083 bp single open reading frame (ORF) encoding a 360 amino acid and 37.64 kD protein. The protein shares homology with homoserine kinase from Arabidopsis thaliana. Sequence alignment indicated that GmHSK contained a conserved motif of GHMP kinase superfamily. Phylogenetic analyses suggested that the HSK in plants could be classified into two groups. To have a global view of the dynamic gene expression pattern during the whole growth period, we analyzed the transcript levels in eight different tissues/organs by qRT-PCR. The results showed that the GmHSK gene was expressed in all vegetative organs and reproductive organs with various levels and fluctuated during the plant development. This data provided a versatile resource to understand the regulation of GmHSK gene during the whole growth period in the high protein crop, soybean, and could aid in the transgenic breeding to improve the content and quality of soybean protein.

Genotypic Diversity at the Lr10 Locus for Leaf Rust Resistance in Various Hexaploid Wheat Varieties (lines)

HAN Shu-Xiao,LIU Quan-Lan,DONG Jie,CHEN Jian-Sheng,TIAN Ji-Chun

Acta Agron Sin. 2013, 39(11):  1983-1991.  doi:10.3724/SP.J.1006.2013.01983

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Genotypes H1 and H2 are two ancient haplotypes on Lr10 locus, which is a resistance gene to wheat leaf rust. They are identified based on the presence of both Lr10 and RGA2 in full length (H1), and the absence of Lr10 and chromatin rearrangement of RGA2 (H2) due to chromosome 1AS reorganization during species evolution. Both haplotypes contain several subhaplotypes. To understand genetic diversity on Lr10 locus, we tested the frequencies of H1 and H2 haplotypes and their subhaplotypes in 189 wheat cultivars and 58 breeding lines originating from various provinces of China. The H2 haplotype was dominant in the developed cultivars and breeding lines with the frequencies of 95.2% (180/189) and 96.6% (56/58), respectively. Five novel subhaplotypes were detected in the developed cultivars, namely H1-2, H2-4, H2-5, H2-6, and H2-7. In cultivars, subhaplotype H2-1 was the most frequent (69.3%), whereas subhaplotypes H2-3 and H2-6 had the lowest frequencies (0.5%). Among the five subhaplotypes detected in breeding lines, subhaplotype H2-1 had the highest frequencies (27.6%), whereas subhaplotypes H1-2 was the least frequent (3.5%). Interestingly, the subhaplotypes except for H2-1 and H2-2 were highly breeding location-dependent (P < 0.05). These results support the hypothesis that both haplotypes have been maintained through a balanced polymorphism mechanism during wheat domestication. Furthermore, the five novel subhaplotypes suggest that genetic diversities resulting from recombination and other types of chromatin reorganizations (e.g., origin of the H2 haplotype and polymorphism for the Lr10 locus) have been going on since the formation of the hexaploid wheat. Significantly, identification of the H1-2 subhaplotype is a clear evidence of occurrence of recombination between the two ancient haplotypes, which disagrees with the previous notion. Importantly, because the frequencies of H1 is lower than 5% in developed cultivars and breeding lines, actions for protecting germplasm with the H1 haplotype are highly recommended.

Mechanism Analysis of Receptor-Like Kinases Gene OsBAK1L Involved in Regulating Cell Death Response of Rice

CHEN Xian-Chao,HUANG Li-Yu,ZHOU Yong-Li

Acta Agron Sin. 2013, 39(11):  1992-1999.  doi:10.3724/SP.J.1006.2013.01992

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Plant receptor-like kinase BAK1 (BRI1-associated kinase 1) plays an important role in Arabidopsis in regulating diverse physiological processes, including development and signals in innate immunity. In the study, we choose a homologous geneLOC_Os03g49620.4in rice and tentatively name it as OsBAK1L for structural and functional study. The result indicates that the OsBAK1L protein is a member of SERKL (Somatic embryogenesis receptor kinase Like) protein family and located in the cell membrane. OsBAK1L was down regulated in OsBAK1L-RNAi transgenic rice plants. When the rice plants were inoculated with the Xanthomonas oryzae pv. oryzicola Rs105, hypersensibility response (HR) was triggered in both the OsBAK1L-RNAi transgenic plants and the resistant 9804-Rxo1 plants, while it was postponed only in OsBAK1L-RNAi transgenic rice plants. The expression pattern of HR associated gene, OsMPK13 (Mitogen activated protein kinase 13), and HR were also delayed in transgenic plants and had the the same changing trends. These results indicate that OsBAK1L might control HR by regulating the expression of OsMPK13.

Genetic Diversity of Tea Germplasm Resources in Yunnan Province Based on Phenotypic Characteristics

JIANG Hui-Bing,SONG Wei-Xi,YI Bing,LI You-Yong,MA Li,CHEN Lin-Bo,TIAN Yi-Ping,DUAN Zhi-Fen,LIU Ben-Ying,LIANG Ming-Zhi

Acta Agron Sin. 2013, 39(11):  2000-2008.  doi:10.3724/SP.J.1006.2013.02000

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We analyzed and compared the genetic diversity of main phenotypic characteristics in 830 tea germplasm, from ten different areas in Yunnan Province. The results showed Section Thea had the rich genetic diversity, the diversity index of descriptive traits was 0.64–1.40, with the average of 1.04, and relatively higher in young shoot color, the lowest in leaf base shape; the diversity index was 0.76–0.99, with the highest in Honghe prefecture, the second in Lincang and Wenshan prefectures, the lowest in Zhaotong prefecture. The variation coefficient of numerical traits was 10.27%–48.14%, with the average of 26.43%, and relatively higher in the ratio of polyphenol to amino acid, and the lowest in water extract; the variation coefficient was 16.09%–25.75%, with the highest in Wenshan and Honghe prefectures, and the lowest in Zhaotong and Dali. The genetic diversity and variation coefficient showed a tendency of Southeast>West>Northeastern in phenotypic characteristics. By cluster analysis, tea germplasm resources from ten regions was divided geographically into three groups, Zhaotong and Honghe for each group respectively, others for the third group. The results demonstrate an obviously ecogeographical differentiation among Southeast, West, and Northeast areas of tea germplasm in Yunnan, and Southeast is the distribution center with genetic diversity in phenotypic characteristics.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Effects of Integrated Agronomic Practices on Nitrogen Efficiency and Soil Nitrate Nitrogen of Summer Maize

JIN Li-Bin,CUI Hai-Yan,LI Bo,YANG Jin-Sheng,DONG Shu-Ting,ZHAO Bin,LIU Peng,ZHANG Ji-Wang

Acta Agron Sin. 2013, 39(11):  2009-2015.  doi:10.3724/SP.J.1006.2013.02009

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A field study with an integrated management experiment and a nitrogen (N) application rate test was conducted to explore the effects of integrated agronomic practices such as sowing methods, sowing time, fertilizers amount and applied date and harvest time on N efficiency and nitrate N of summer maize,. Results showed that, with increasing N application amount partial factor productivity of applied N increased and N fertilizer agricultural utilization efficiency decreased significantly; N use efficiency and N harvest index increased first and then decreased gradually, and both of them reached the maximum at a N application of 184.5 kg ha^-1; the N accumulation before tasseling stage and nitrate N accumulation in 0–30 cm soil increased. That means that it is difficult to realize high N efficiency and lower soil N accumulation persistently. Under integrated management of further high yield and high efficiency treatment (Opt-2), the partial factor productivity of applied N, N fertilizer agricultural utilization efficiency, N use efficiency and N harvest index all increased significantly; the N accumulation before tasseling stage was low, but the N accumulation of plants was higher than that under farmers’ traditional cultivation and lower than that under high yield treatment at harvest time; after harvesting, the nitrate N accumulation in 0–30, 30–60, and 60–90 cm soils was lower than that under farmers’ practices. Therefore the N efficiency of summer maize was increased significantly and the N accumulation trend was reasonable in growing season and the soil nitrate N accumulation was lower after harvesting when the integrating agronomic practices are performed.

Influence of Maize-soybean Rotation and N fertilizer on Bacterial Community Composition

ZHOU Lan,YANG Yong,WANG Zhan-Hai,CHEN Fu,ZENG Zhao-Hai

Acta Agron Sin. 2013, 39(11):  2016-2022.  doi:10.3724/SP.J.1006.2013.02016

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In soybean flowering period, took rhizosphere soil samples from three treatments including continuous cropping soybean (soybean-soybean-soybean), maize-soybean rotation I(soybean-maize-soybean) and maize-soybean rotation II (maize-maize-soybean). Each treatment had three levels of nitrogen application including 0, 50 and 100 kg ha^-1. Soil microbial community changes under maize-soybean rotation system and various nitrogen applications were investigated by the techniques of denaturing gradient gel electrophoresis (DGGE) analysis. The results showed that the biological diversity and abundance of three kinds of soil microbial community had a decline trend along with the increase of nitrogen application levels. Under high nitrogen application level (100 kg ha^-1), a significant decrease in diversity and abundance of rhizosphere soil microbial communities was observed in both continuous cropping soybean system and maize-soybean rotation II system. And in maize-soybean rotation I system, there was only a slightly decrease in diversity and abundance of rhizosphere soil microbial communities. Therefore, 1-year maize in rotation with soybean (soybean-maize-soybean) can alleviate the effect of nitrogen fertilizer on rhizosphere soil microbial diversity and richness, but the effect of nitrogen application significantly changed its bacterial community structure. Maize-soybean rotation II system (maize-maize-soybean) was less affected by nitrogen fertilizer and showed relatively high stability. In addition, in those three kinds of soil, there were the categories of Acidobacteria, Proteobacteria and Firmicutes, in which, Acidobacteria and Proteobacteria were predominant.

Responses of Antioxidant Enzyme and PSII Electron Transport in Leaf of Transgenic Tobacco Carrying 2-Cys Prx to Salt and Light Stresses

ZHANG Hui-Hui,TIAN Qi,LIU Guan-Jun,HU Yan-Bo,WU Xiang-Yu,TIANA Ye,LI Xin,SUN Guang-Yu

Acta Agron Sin. 2013, 39(11):  2023-2029.  doi:10.3724/SP.J.1006.2013.02023

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2-Cys peroxiredoxins (2-Cys Prxs) in plants were reported to localize to plant chloroplasts and perform antioxidative function during plant development and photosynthesis. This paper investigated the function of tobacco 2-Cys Prx gene overexpressed in transgenic tobacco (Nicotiana tabacum) plants with tolerance against light intensity and salt stresses. The results showed that superoxide dismutase (SOD) activity in leaves of two types of tobacco increased under weak light (200 μmol m^–2 s^–1) and salt stresses, ascorbateperoxidase (APX) activity changed little, and the content of H₂O₂ slightly increased. Salt stress enhanced SOD activity and decreased APX activity under strong light (1000 μmol m^–2 s^–1). The content of H₂O₂ in leaves of transgenic tobacco with 2-Cys Prx increased slower than that of wild tobacco. The electron transport rate (ETR), PSII photochemical efficiency (F_v/F_m) and actual photochemical efficiency (Ф_PSII) in leaves of transgenic tobacco with 2-Cys Prx were higher than those of control under high light. Electron transports in the receptor side were lower than that in control. The results suggested that 2-Cys Prx could be the effective removal of excess H₂O₂ while APX activity decreasedunder high light and salt stresses, and could reduce PSII photoinhibition induced by high light and salt stresses.

Changes of Photosynthetic Membrane Function and Protein Complexes in Flag Leaves of Liangyoupeijiu during Leaf Senescence

YE Lu-Huan,SHEN Wei-Jun,ZHENG Bao-Gang,SONG Tao,CHEN Guo-Xiang,Lü Chuan-Gen

Acta Agron Sin. 2013, 39(11):  2030-2038.  doi:10.3724/SP.J.1006.2013.02030

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The purpose of this study was to explore the content variation of thylakoid membrane protein complexes and its relationship with light absorption, transformation and transfer in flag leaves of high-yield hybrid rice Liangyoupeijiu during senescence. A rice cultivar, Liangyoupeijiu was grown in the field. Through chlorophyll a fluorescence transient, physiological and biochemical techniques, we studied the function of photosynthetic membrane. The content changes of thylakoid membrane protein complexes were also investigated by Blue-Native polyacrylamide gel-electrophoresis (BN-PAGE). The results showed that chlorophyll content, photosynthesis and thylakoid membrane protein content of flag leaves rose and peaked at heading stage, then began to decline. It still maintained a high level at flowering and filling stages, and the significant decline appeared untill the stage of milky and wax ripeness. The stability of protein complexes (i.e. inverse degradation rate) during leaf senescence showed an order of LHCII > PSIIcore > PSIcore > ATPase & Cyt b₆/f > LHCI. Protein complexes and electron transport activity of PSIdeclined later but more quickly than those of PSII. The decreased chlorophyll a/b ratio could be explained by the relative enrichment of light-harvesting antenna to reaction center with leaf senescence. The stable LHCII kept the high level of absorbing energy in the late of flag leaf growth, which may play an important role in adjusting the energy distribution and dissipation during leaf senescence.

Short-medium Term Preservation of Rice Suspension Cells

GAO Yi-Ping,Lü Meng-Yu,ZHAO He,YANG Xue-Ju,WANG Hai-Bo

Acta Agron Sin. 2013, 39(11):  2039-2045.  doi:10.3724/SP.J.1006.2013.02039

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The preservation of cell suspension in short-medium term is widely needed in cell biology. In this paper, the preservation efects of cell suspension of rice cultivar Zhonghua 15 on AA, N6, and MS solid culture media were compared. The results showed that AA medium was suitable for suspension cells preservation. The cell suspension still kept resuspensible after growing continuously on AA solid medium for 4 months, and then on AA medium supplemented with 0.5 mg L^-1 2,4-D for 6 months (subcultured at about 45 d interval). Three kinds of methods of suspension cells preservation, namely preservation on AA solid medium, cryopreservation, and continuously suspending culture, were compared. The results indicated that the first method kept good suspensible property, had high regeneration rate, and had a little influence on activity of POD and SOD, even though the suspension cells grew on AA medium for 2–9 months. AA solid medium is ideal for the preservation of suspension cells in short-middle-term.

CodA Transgenic Tomato Plants Enhance Tolerance to High Temperature Stress

LI Zhi-Mei,DOU Hai-Ou,WEI Dan-Dan,MENG Qing-Wei,CHEN Tony Huihuang,YANG Xing-Hong

Acta Agron Sin. 2013, 39(11):  2046-2054.  doi:10.3724/SP.J.1006.2013.02046

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The effects of codA gene on photosynthesis, activities of antioxidative enzymes, the expression of the heat response genes and the accumulation of D1 protein 50℃ respectively for two hours, then net photosynthetic rate (P_n), the maximal efficiency of PSII photochemistry (F_v/F_m), hydrogen peroxide (H₂O₂) content, malondialdehyde (MDA) content, relative electric conductivity (REC) and activities of antioxidativeenzymes were detected. After 42℃ heat stress for 0, 3, 6 hours, the expressions ofantioxidant enzyme genes and heat stress genes and the accumulation of the D1 protein were also determined. The results demonstrated that under high temperature stress, the inhibition degree of P_n and F_v/F_m in codA transgenic tomato plants was lower than that in wild type plants. The accumulation of H₂O₂, MDA and REC in codA transgenic tomato plants was less than that in wild type plants. And codA transgenic tomato plants also greatly enhanced the activities of catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX). Moreover, the expression levels of antioxidant genes and heat response genes in codA transgenic tomato plants was higher than those in wild type plants and the degradation degree of D1 protein in codA transgenic tomato plants were lower than that in wild type plants. It indicated that codA transgenic tomato plants enhance thermotolerance via maintaining higher activities of antioxidant enzymes, accelerating the expression of heat response genes and reducing the degradation of D1 protein. in tomato leaf under different temperature stresses were investigated to reveal the mechanism of thermotolerance in codA-transgenic tomato plants. The wild type (cv. Moneymaker) and codA transgenic tomato plants were treated with 25, 30, 35, 40, 45, and

Comparison of Microecological Characterization in Rhizosphere Soil between Healthy and Un-healthy Plants in Continuous Cropping Potato Fields

CHEN Jie,GUO Tian-Wen,TAN Xue-Lian,ZHU Wei-Bing,WEI Xiao-Li,WANG Dong-Sheng,XUE Quan-Hong

Acta Agron Sin. 2013, 39(11):  2055-2064.  doi:10.3724/SP.J.1006.2013.02055

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To explore the microecological mechanism of healthy plant growth in continuous potato fields in Gansu Province, China, we measured contents of available soil nitrogen (NH₄⁺-N), phosphorus (P), and potassium (K) using conventional soil nutrient analytic methods, abundance of soil actinomycetes using serial dilution and plating techniques, and screened antagonistic actinomycetes from obtained actinomycete isolates using the agar block method. The selected dominant actinomycetes were identified by 16S rRNA sequence analysis, and the inhibitory effect of one dominant actinomycete, Streptomyces gancidicus, was tested using culture filtrate. Results showed that in the four-year continuous potato field, available soil P and K contents in the rhizosphere of diseased plants were respectively 29.9% and 12.5% lower than those of healthy plants, whereas soilNH₄⁺-N content in the rhizosphere of diseased plant was 24.1% higher than that of healthy plant. Compared with those fromthe rhizosphere of healthy plants, the number of soil actinomycetes, Micromonospora, and unidentified actinomycetes from the rhizosphere of diseased plants cultured with the Gause1 medium decreased by 51.1%, 83.0%, and 53.9%, respectively, whereas the number of soil actinomycetes and Streptomyces from the rhizosphere of diseased plants cultured with the Humic Acid medium decreased by 46.0% and 46.7%, respectively. The soil actinomycetes antagonistic potentiality (SAAP) of actinomycetes with antagonistic effects on thefour pathogenic fungi of potato were lower in the rhizosphere of diseased plants than in the rhizosphere of healthy plants. S. gancidicus and S. galilaeus were found dominant in the rhizosphere of healthy and diseased plants, respectively. In conclusion, the microecology of rhizosphere soil that supports healthy plant growth in the continuous potato field is mainly characterized by: available nutrient combination of abundant P and K with relatively poor N contents; and a larger number of soil actinomycetes than that of diseased plants, with the numerically dominant actinomycetes showing beneficial antagonistic effect on several common soil-borne pathogenic fungi.

Effects of Low-light Stress on Male and Female Flower Development and Pollination and Fructification Ability of Different Maize (Zea mays L.) Genotypes

ZHOU Wei-Xia,WANG Xiu-Ping,MU Xin-Yuan,LI Chao-Hai

Acta Agron Sin. 2013, 39(11):  2065-2073.  doi:10.3724/SP.J.1006.2013.02065

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A split plot experiment was conducted under field conditions to study the effects of low-light stress on the ear and tassel development, pollination and seed-setting rate using two maize (Zea mays L.) hybrids (low light sensitive hybrid Yuyu22 and low light tolerant hybrid Zhengdan958). Low-light stress from three days before tasselling to ten days after silking was obtained using 50% transmittance shading nets. The results showed that low-light stress caused a slowdown of ear and tassel growth and development rate, delayed the tasselling date, silking date and full flowering date, prolonged the anthesis-silking interval (ASI). Daily pollen quantity was higher under low-light stress than that of the control at silking with a larger difference compared with the low light sensitive hybrid. For the low light sensitive hybrid under low light stress, reticula and gaps in the surface of pollen were increased, pollen aperture and its near part were severely deformed with significantly retraction, nutrient supply was reduced due to the reduction of starch grains in the pollen. While for the low light tolerant hybrid under low light stress, pollen surface characters were similar to those of the control, with a little retraction of the pollen aperture and decrease of starch grain density in the pollen. Under low light stress, pollen activity, pollen emergence rate and pollen tube growth rate of the low light sensitive hybrid decreased while those of the low light tolerant hybrid increased. Silk elongation rate and number of silks emerged from the husks were decreased and decreased more in the ear tip than in the ear base. Ear length and kernel number per ear decreased in both hybrids and decreased more in low light sensitive hybrid. Prolonged ASI, deformed pollen, reduction of nutrient supply in pollen, decreased silk elongation rate and number of silks emerged from the husks, and the decrease of kernel IAA content and the increase of kernel ABA content were the primary causes leading to the reduction of ear kernel number.

Effect of Drought Stress on Agronomic Traits and Quality and WUE in Different Colored Upland Cotton Cultivars

CHEN Yu-Liang,SHI You-Tai,LUO Jun-Jie,LI Zhong-Wang,HOU Yi-Qing,WANG Di

Acta Agron Sin. 2013, 39(11):  2074-2082.  doi:10.3724/SP.J.1006.2013.02074

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To explore the effect of drought stress on main colored cotton traits and the water use efficiency (WUE) mechanism, we performed the experiments with split-plot design, irrigation amounts (normal irrigation, stress irrigation, and no irrigation) were taken as the main-plots, and seven colored cotton cultivars were used as the sub-plots. The results showed that the boll number per plant, weight per boll, plant height, leaf number, number of fruiting branch, harvest index, number of fruit nodes, seed index, stem diameter, internode length of fruit branches and main stem reduced, but the lint percentage increased under drought stress. When the irrigation amount reduced by half, all cultivars yield decreased, there was significant difference between normal irrigation and no irrigation (P<0.05). There also existed significant difference in seed cotton yield among cultivars (P<0.05), the yield reduction of brown cotton cultivar was higher than that of green cotton cultivar. Under normal irrigation, the WUE of white cotton was higher than that of green cotton and brown cotton; there was no significant difference in WUE between brown cotton and green cotton. Under drought stress, the WUE of brown cotton was higher than that of green cotton. So WUE is related to leaf number, the boll number per plant, number of fruiting branches, number of fruit nodes, plant height, harvest index, weight per boll, length between fruit branches and main stem, seed index, the stem diameter, and lint percentage.

Dynamic Changes of Endogenous Hormones Content and Dry Matter Accumulation of Pods and Kernels in Different Varieties (Lines) of Peanut (Arachis hypogaea L.)

LUO Bing,LIU Feng-Zhen,WAN Yong-Shan,ZHANG Kun,ZHAO Wen-Xiang

Acta Agron Sin. 2013, 39(11):  2083-2093.  doi:10.3724/SP.J.1006.2013.02083

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Endogenous hormones play important roles in plant growth and development , and yield formation. To reveal the relationship between dry matter accumulation and hormones content in developing pods and kernels,  we conducted an experiment using three peanut varieties (lines) with normal seeds and one wrinkled mutant line 05D677. The main results were as follows: (1) The period of 24–60 days after peg penetration was a rapid dry weight accumulation phase, during which the average of both pod dry matter accumulation rate (_PK_W) and the corresponding kernel dry matter accumulation rate (_KK_W) of Shanhua 15, 05D610 and Baisha 1016 was significantly higher than that of 05D677; the _PK_W and _KK_W of the three normal varieties peaked at 30 days, different from those of 05D677 at 36 days. (2) The four varieties shared much the same dynamic changes trends of cytokinin (Z+ZR), gibberellin (GA), auxin (IAA) and abscisic acid (ABA) in the young pods or kernels. However, GA content of 05D677 peaked six days later than that of other three normal varieties; the peak values of Z+ZR, GA and ABA contents of 05D677 were all very significantly lower than those of other three, while the opposite result was discovered as to IAA content. (3) In the middle and late periods of pod expansion, Z+ZR, GA and ABA contents were in very significantly positive correlation with _PK_W and _KK_W, while the opposite for IAA content. Z+ZR content had very significantly positive correlation with _PK_W and _KK_W in the early pod filling period, and the same result was found between GA content and _PK_W in the late filling and mature period. ABA content had very significantly negative correlation with _PK_W and _KK_W in the late pod filling, while had a very significantly positive correlation with _PK_W in the mature period. (4) Compared with other three normal cultivars, IAA content of 05D677 was significantly increased in the early pod and kernel expansion period accompanied by insufficient Z+ZR, GA and ABA contents, and the proportion imbalances of endogenous hormones possibly led to development process delay and significantly reduced dry matter accumulation rate of pods and kernels, which may be the reason for plumpness shortage and shrink seeds of 05D677.

RESEARCH NOTES

Molecular Detection and Take-all Response Assays of TiERF1-RC7 Transgenic Wheat

LIU Fei,YANG Li-Hua,WANG Ai-Yun,MA Xiao-Fei,DU Li-Pu,LIU Xin,LI Pan-Song,ZHANG Zeng-Yan,MA Ling-Jian

Acta Agron Sin. 2013, 39(11):  2094-2098.  doi:10.3724/SP.J.1006.2013.02094

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The aim of this study was to understand the role of TiERF1 and RC7 genes in wheat defense response to take-all. Both genes were simultaneously transformed into wheat cultivar Yangmai 18. The resistance to talk-all in five transgenic lines were analyzed by PCR and RT-PCR methods, and evaluated by artificial inoculation in greenhouse and field tests. Scanning electron microscope technique was used to observe the morphology and number of the pathogen mycelia on the root surfaces of resistant transgenic and susceptible receptor wheat plants. The PCR assay showed that both TiERF1 and RC7 genes were integrated into the transgenic lines and inherited to the T₃ generation. The RT-PCR assay confirmed expressions of both genes in the transgenic lines. The results showed that five transgenic lines exhibited stable and efficient resistance to take-all with disease severity lower than 10% at seedling stage in greenhouse and rate of white spike lower than 13% at maturity in field. In the contrast of Yangmai18, the severity was 62.98%, rate of white spike was 26.09%. Electron microscope observation revealed that the number and growth tendency of hyphae on roots of the resistant transgenic wheat were significantly lower and weaker than those of the wild type. The expressions of TiERF1 and RC7 inhibit the growth of pathogen hyphae in the transgenic wheat plants, leading to improved resistance to take-all.

Sucrose Accumulation and Key Enzyme Activities in Different Parts of Seed in Vegetable Soybean

LI Yan-Sheng,NAN Hai-Yang,DU Ming,LIAN Teng-Xiang,ZHANG Qiu-Ying,LIU Xiao-Bing

Acta Agron Sin. 2013, 39(11):  2099-2105.  doi:10.3724/SP.J.1006.2013.02099

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Three vegetable soybean varieties with different soluble sugar contents were grown in field condition. Sucrose contents and four critical enzymes activities in different parts of seed were analyzed at R5.5, R6, R6.2, R6.5, and R7 stages, respectively. Sucrose contents of different seed parts increased at early seed filling stage and then decreased at late stage with the peak value at R6.2 stage. Sucrose content in hypocotyl was 57.6%, 53.6%, 44.2% greater than that of cotyledon, and 71.6%, 75.3%, 73.6% greater than that of seed coat at R6.2 stage for the three varieties, respectively. The cotyledon contributed 90% dry weight to the total seed dry weight, and thus the sucrose content of the whole seed was primarily determined by sucrose content in cotyledon. Cotyledon had the highest activity of sucrose phosphate synthase (SPS). The cotyledon SPS activity of cv. 121 was much higher than that of the other two varieties. The sucrose synthase (SS) activity of different seed parts was higher in early seed filling stage than in late filling stage. The highest value of SS activity was observed in hypocotyl at R5.5 stage. Greater differences were found between acid invertase (AI) and neutral invertase (NI) activities. NI activity was higher in early seed filling stage and then decreased till R7 stage. Significant differences were observed for AI activities among three seed parts at the same seed filling stage but there were no differences for NI activities. AI activity in seed coat was much higher than that in hypocotyl and cotyledon. Negative relationship was found between AI activity and sucrose content in seed coat (r= –0.59^**). The correlation analysis between sucrose accumulation and four critical enzymes activities showed that seed sucrose content was not controlled dominantly by one enzyme. The difference between sucrose synthesis enzyme activity (SPS) and sucrose decomposition enzyme activity (SS+AI+NI) was positively correlated with seed sucrose accumulation (r=0.53^**).